We discuss the necessity and demonstrate the validity of introduction the notion of deterministic chaos in quantum field theory. Brief review of the existing approaches to this problem is given. We compare proposed chaos criterion for quantum fields with existing ones. Its consequences in particle physics are also discussed. §1. IntroductionChaos phenomenon attracts much attention in various fields of natural sciences, from celestial mechanics 1) ( pp.349-359) and behavior of social systems 2) to quantum mechanics 3) and atomic physics. 4) Though the understanding of the reasons and regimes of chaotic behavior in classical (Hamiltonian) systems is already achieved in main, 5) problems connected with properties, manifestations and even definition of deterministic chaos in quantum world are still basically open. 6), 7) Prevalence of chaotic motions in the majority of natural phenomena explains the fundamental and applied significance of its study. Particulary, chaotic behavior is intrinsical to classical gauge fields in modern theories of particle interactions 8), 9), 10) as well it plays crucial role for quantum tunneling control, which is of practical importance. 11)In this paper we discuss chaos phenomenon in the context of quantum field theory (QFT). We premise the consideration of our main topic by some motivations. Investigation of the classical gauge field dynamics from the viewpoint of chaos was started in a few years after recognition of gauge theories based on SU (3) and SU (2) ⊗ U (1) groups as theories of strong and electroweak interactions respectively. Nonabelian gauge fields form complicated nonlinear system with large number of degrees of freedom, which behavior demonstrates a lot of regimes when parameters vary. Besides the investigation of classical gauge fields to be interesting from the viewpoint of nonlinear dynamics, it is also important from the viewpoint of particle physics (particulary QCD), where large progress is achieved in understanding of perturbative phenomena, but comparatively little is known about the non-perturbative evolution of quarks and gluons. Namely, the confinement phenomenon responsible for absence of free colored objects is waiting for its explanation (however a lot of results is obtained in this direction, for review see Ref. 12) ). The problem is that there are no exact methods for description of non-perturbative evolution of quantum fields, when coupling between them is not too small (there is no small parameter) and perturbative expansions can not be applied. The first step for understanding of quantum dynamics in this coupling regime is the investigation of the classical behavtypeset using PTPT E X.cls Ver.0.89